diff --git a/Sprint-1/fix/median.js b/Sprint-1/fix/median.js
index 5c5b796e1..d272d61af 100644
--- a/Sprint-1/fix/median.js
+++ b/Sprint-1/fix/median.js
@@ -5,10 +5,42 @@
 // Hint: Please consider scenarios when 'list' isn't an array, is empty,
 // or contains values that aren't numbers (the function is expected to throw - see the tests).
 
-function calculateMedian(list) {
+function calculateMedian(list = 0) {
+  if (list === null) {
+    throw new Error("calculateMedian requires an array of numbers");
+  }
+
+  if (list.length === 0) {
+    throw new Error("calculateMedian requires a non-empty array");
+  }
+
+  if (typeof list === "string") {
+    throw new Error("calculateMedian requires an array of numbers");
+  }
+
+  if (typeof list === "number") {
+    throw new Error("calculateMedian requires an array of numbers");
+  }
+
+  if (typeof list === "object" && !Array.isArray(list)) {
+    throw new Error("calculateMedian requires an array of numbers");
+  }
+
+  for (item of list) {
+    if (typeof item === "string" || item === null || item === undefined) {
+      throw new Error("calculateMedian requires an array of numbers");
+    }
+  }
+
+  const sortedList = list.toSorted((a, b) => a - b);
+
   const middleIndex = Math.floor(list.length / 2);
-  const median = list.splice(middleIndex, 1)[0];
-  return median;
+
+  if (list.length % 2 === 0) {
+    return (sortedList[middleIndex - 1] + sortedList[middleIndex]) / 2;
+  }
+
+  return sortedList[middleIndex];
 }
 
 module.exports = calculateMedian;
diff --git a/Sprint-1/implement/dedupe.js b/Sprint-1/implement/dedupe.js
index 781e8718a..999b81e16 100644
--- a/Sprint-1/implement/dedupe.js
+++ b/Sprint-1/implement/dedupe.js
@@ -1 +1,13 @@
-function dedupe() {}
+function dedupe(elements) {
+  const dedupedArr = [];
+
+  for (element of elements) {
+    if (!dedupedArr.includes(element)) {
+      dedupedArr.push(element);
+    }
+  }
+
+  return dedupedArr;
+}
+
+module.exports = dedupe;
diff --git a/Sprint-1/implement/dedupe.test.js b/Sprint-1/implement/dedupe.test.js
index d7c8e3d8e..9f9caae20 100644
--- a/Sprint-1/implement/dedupe.test.js
+++ b/Sprint-1/implement/dedupe.test.js
@@ -16,13 +16,34 @@ E.g. dedupe([1, 2, 1]) returns [1, 2]
 // Given an empty array
 // When passed to the dedupe function
 // Then it should return an empty array
-test.todo("given an empty array, it returns an empty array");
+it("given an empty array, returns empty array", () => {
+  expect(dedupe([])).toEqual([]);
+});
 
 // Given an array with no duplicates
 // When passed to the dedupe function
 // Then it should return a copy of the original array
+it("given array without duplicates, returns that array", () => {
+  expect(dedupe([4, 6, 9, 23])).toEqual([4, 6, 9, 23]);
+});
 
 // Given an array of strings or numbers
 // When passed to the dedupe function
-// Then it should return a new array with duplicates removed while preserving the 
+// Then it should return a new array with duplicates removed while preserving the
 // first occurrence of each element from the original array.
+it("given array with duplicates, returns array without duplicates", () => {
+  expect(dedupe([4, 6, 9, 23, 9, 23, 23])).toEqual([4, 6, 9, 23]);
+  expect(dedupe([4, "Hi", 9, "Hi", 9, 23, 23, "hi"])).toEqual([
+    4,
+    "Hi",
+    9,
+    23,
+    "hi",
+  ]);
+  expect(dedupe(["Hi", "Hi", "hi", "bye", "Hi", "bye", "yes"])).toEqual([
+    "Hi",
+    "hi",
+    "bye",
+    "yes",
+  ]);
+});
diff --git a/Sprint-1/implement/describe-median.js b/Sprint-1/implement/describe-median.js
index 3381cfc0a..e6a0a4033 100644
--- a/Sprint-1/implement/describe-median.js
+++ b/Sprint-1/implement/describe-median.js
@@ -20,6 +20,13 @@ function calculateMedian(list) {
 }
 
 // Implement this function. See describe-median.test.js for the acceptance criteria.
-function describeMedian(list) {}
+function describeMedian(list) {
+  try {
+    const median = calculateMedian(list);
+    return "The median is " + median;
+  } catch (error) {
+    return "Could not calculate a median: " + error.message;
+  }
+}
 
 module.exports = describeMedian;
diff --git a/Sprint-1/implement/describe-median.test.js b/Sprint-1/implement/describe-median.test.js
index e7d18a264..6ce2adc8a 100644
--- a/Sprint-1/implement/describe-median.test.js
+++ b/Sprint-1/implement/describe-median.test.js
@@ -21,12 +21,30 @@ const describeMedian = require("./describe-median.js");
 // When passed to describeMedian
 // Then it should return "The median is " followed by the median
 // Delete this test.todo and replace it with a test.
-test.todo('given [1, 2, 3], returns "The median is 2"');
+it("Given array of positive numbers, it returns the correct message", () => {
+  expect(describeMedian([1, 2, 6])).toEqual("The median is 2");
+});
 
 // Given an empty array
 // When passed to describeMedian
 // Then it should return "Could not calculate a median: calculateMedian requires a non-empty array"
+it("Given an empty array, it tells you it couldn't calculate the median and why", () => {
+  expect(describeMedian([])).toEqual(
+    "Could not calculate a median: calculateMedian requires a non-empty array"
+  );
+});
 
 // Given something that isn't an array of numbers, e.g. "banana"
 // When passed to describeMedian
 // Then it should return "Could not calculate a median: calculateMedian requires an array of numbers"
+it("Given something that isn't array of numbers, it tells you it couldn't calculate the median and why", () => {
+  expect(describeMedian("banana")).toEqual(
+    "Could not calculate a median: calculateMedian requires an array of numbers"
+  );
+  expect(describeMedian([3, "5", 8])).toEqual(
+    "Could not calculate a median: calculateMedian requires an array of numbers"
+  );
+  expect(describeMedian(42)).toEqual(
+    "Could not calculate a median: calculateMedian requires an array of numbers"
+  );
+});
diff --git a/Sprint-1/implement/max.js b/Sprint-1/implement/max.js
index 6dd76378e..f10e67d8c 100644
--- a/Sprint-1/implement/max.js
+++ b/Sprint-1/implement/max.js
@@ -1,4 +1,24 @@
 function findMax(elements) {
+  if (!Array.isArray(elements)) {
+    throw new Error("findMax requires an array of numbers");
+  }
+
+  if (elements.length === 0) {
+    return -Infinity;
+  }
+
+  let max = elements[0];
+
+  for (element of elements) {
+    if (typeof element != "number") {
+      throw new Error("findMax requires an array of numbers");
+    }
+    if (element > max) {
+      max = element;
+    }
+  }
+
+  return max;
 }
 
 module.exports = findMax;
diff --git a/Sprint-1/implement/max.test.js b/Sprint-1/implement/max.test.js
index ff3fbb5e5..84e9830cd 100644
--- a/Sprint-1/implement/max.test.js
+++ b/Sprint-1/implement/max.test.js
@@ -16,28 +16,58 @@ const findMax = require("./max.js");
 // When passed to the max function
 // Then it should return -Infinity
 // Delete this test.todo and replace it with a test.
-test.todo("given an empty array, returns -Infinity");
+it("given an empty array, returns -Infinity", () => {
+  expect(findMax([])).toEqual(-Infinity);
+});
 
 // Given an array with one number
 // When passed to the max function
 // Then it should return that number
+it("Given array with one number should return that number", () => {
+  expect(findMax([3])).toEqual(3);
+});
 
 // Given an array with both positive and negative numbers
 // When passed to the max function
 // Then it should return the largest number overall
+it("Given array of positive and negative values returns the biggest", () => {
+  expect(findMax([4, -7, 47, -90])).toEqual(47);
+});
 
 // Given an array with just negative numbers
 // When passed to the max function
 // Then it should return the closest one to zero
+it("Given array of negative values returns the closest to zero", () => {
+  expect(findMax([-4, -7, -47, -90])).toEqual(-4);
+});
 
 // Given an array with decimal numbers
 // When passed to the max function
 // Then it should return the largest decimal number
+it("Given array of positive and negative values returns the biggest", () => {
+  expect(findMax([4.3, -7.83, 47.134, -90.2947])).toEqual(47.134);
+});
 
 // Given an array containing a value that isn't a number
 // When passed to the max function
 // Then it should throw Error("findMax requires an array of numbers")
+it("Given array with value that isn't a number, should throw", () => {
+  expect(() => {
+    findMax([5, "ooo", 203]);
+  }).toThrow("findMax requires an array of numbers");
+});
 
 // Given something that isn't an array at all, such as "hey", 42 or no argument
 // When passed to the max function
 // Then it should throw Error("findMax requires an array of numbers")
+it("Given argument that isn't an array, should throw", () => {
+  expect(() => {
+    findMax("hey");
+  }).toThrow("findMax requires an array of numbers");
+  expect(() => {
+    findMax(42);
+  }).toThrow("findMax requires an array of numbers");
+  expect(() => {
+    findMax();
+  }).toThrow("findMax requires an array of numbers");
+});
diff --git a/Sprint-1/implement/mean.js b/Sprint-1/implement/mean.js
index 36909ea1f..47a471137 100644
--- a/Sprint-1/implement/mean.js
+++ b/Sprint-1/implement/mean.js
@@ -1,3 +1,21 @@
-function calculateMean(list) {}
+function calculateMean(list) {
+  if (!Array.isArray(list)) {
+    throw new Error("calculateMean requires an array of numbers");
+  }
+  if (list.length === 0) {
+    throw new Error("calculateMean requires a non-empty array");
+  }
+
+  let sum = 0;
+
+  for (item of list) {
+    if (typeof item != "number") {
+      throw new Error("calculateMean requires an array of numbers");
+    }
+    sum += item;
+  }
+
+  return sum / list.length;
+}
 
 module.exports = calculateMean;
diff --git a/Sprint-1/implement/mean.test.js b/Sprint-1/implement/mean.test.js
index 847b88676..634d8b5b4 100644
--- a/Sprint-1/implement/mean.test.js
+++ b/Sprint-1/implement/mean.test.js
@@ -23,28 +23,65 @@ const calculateMean = require("./mean.js");
 // When passed to calculateMean
 // Then it should return their mean
 // Delete this test.todo and replace it with a test.
-test.todo("given [1, 2, 6], returns 3");
+it("Given array of positive numbers, it returns their mean", () => {
+  expect(calculateMean([1, 2, 6])).toEqual(3);
+});
 
 // Given an array with a single number
 // When passed to calculateMean
 // Then it should return that number
+it("Given array of one number, it returns that number", () => {
+  expect(calculateMean([2])).toEqual(2);
+});
 
 // Given an array containing negative or decimal numbers
 // When passed to calculateMean
 // Then it should return the correct mean
+it("Given array of negative or decimal number, it returns their mean", () => {
+  expect(calculateMean([1, -2, 6, 5.89, -43.284])).toEqual(-6.4788);
+});
 
 // Given an empty array
 // When passed to calculateMean
 // Then it should throw Error("calculateMean requires a non-empty array")
+it("Given an empty array, it should throw", () => {
+  expect(() => {
+    calculateMean([]);
+  }).toThrow("calculateMean requires a non-empty array");
+});
 
 // Given a value that isn't an array, e.g. "banana", 42, null or {}
 // When passed to calculateMean
 // Then it should throw Error("calculateMean requires an array of numbers")
+it("Given value that isn't array, it should throw", () => {
+  expect(() => {
+    calculateMean("banana");
+  }).toThrow("calculateMean requires an array of numbers");
+  expect(() => {
+    calculateMean(42);
+  }).toThrow("calculateMean requires an array of numbers");
+  expect(() => {
+    calculateMean(null);
+  }).toThrow("calculateMean requires an array of numbers");
+  expect(() => {
+    calculateMean({});
+  }).toThrow("calculateMean requires an array of numbers");
+});
 
 // Given no argument at all
 // When passed to calculateMean
 // Then it should throw Error("calculateMean requires an array of numbers")
+it("Given no value at all, it should throw", () => {
+  expect(() => {
+    calculateMean();
+  }).toThrow("calculateMean requires an array of numbers");
+});
 
 // Given an array containing a non-number value, e.g. [1, "2", 3]
 // When passed to calculateMean
 // Then it should throw Error("calculateMean requires an array of numbers")
+it("Given array containing non-number, it should throw", () => {
+  expect(() => {
+    calculateMean([1, "2", 3]);
+  }).toThrow("calculateMean requires an array of numbers");
+});
diff --git a/Sprint-1/implement/sum.js b/Sprint-1/implement/sum.js
index 9062aafe3..f2a635262 100644
--- a/Sprint-1/implement/sum.js
+++ b/Sprint-1/implement/sum.js
@@ -1,4 +1,18 @@
 function sum(elements) {
+  if (!Array.isArray(elements)) {
+    throw new Error("sum requires an array of numbers");
+  }
+
+  let theSum = 0;
+
+  for (element of elements) {
+    if (typeof element != "number") {
+      throw new Error("sum requires an array of numbers");
+    }
+    theSum += element;
+  }
+
+  return theSum;
 }
 
 module.exports = sum;
diff --git a/Sprint-1/implement/sum.test.js b/Sprint-1/implement/sum.test.js
index a288e0f0a..946a47f3b 100644
--- a/Sprint-1/implement/sum.test.js
+++ b/Sprint-1/implement/sum.test.js
@@ -13,24 +13,51 @@ const sum = require("./sum.js");
 // Given an empty array
 // When passed to the sum function
 // Then it should return 0
-test.todo("given an empty array, returns 0")
+it("given an empty array, returns 0", () => {
+  expect(sum([])).toEqual(0);
+});
 
 // Given an array with just one number
 // When passed to the sum function
 // Then it should return that number
+it("given array with one number, returns that number", () => {
+  expect(sum([6])).toEqual(6);
+});
 
 // Given an array containing negative numbers
 // When passed to the sum function
 // Then it should still return the correct total sum
+it("given array with negative numbers, returns the correct sum", () => {
+  expect(sum([6, -10, 3, 5])).toEqual(4);
+});
 
 // Given an array with decimal/float numbers
 // When passed to the sum function
 // Then it should return the correct total sum
+it("given array with decimal numbers, returns the correct sum", () => {
+  expect(sum([6, 3.68, 3, 5])).toEqual(17.68);
+});
 
 // Given an array containing a value that isn't a number
 // When passed to the sum function
 // Then it should throw Error("sum requires an array of numbers")
+it("given array with values that aren't numbers, should throw", () => {
+  expect(() => {
+    sum([6, 3.68, 3, "hey", 5]);
+  }).toThrow("sum requires an array of numbers");
+});
 
 // Given something that isn't an array at all, such as "hey", 42 or no argument
 // When passed to the sum function
 // Then it should throw Error("sum requires an array of numbers")
+it("Given argument that isn't an array, should throw", () => {
+  expect(() => {
+    sum("hey");
+  }).toThrow("sum requires an array of numbers");
+  expect(() => {
+    sum(42);
+  }).toThrow("sum requires an array of numbers");
+  expect(() => {
+    sum();
+  }).toThrow("sum requires an array of numbers");
+});
diff --git a/Sprint-1/refactor/includes.js b/Sprint-1/refactor/includes.js
index 29dad81f0..cef2f4b62 100644
--- a/Sprint-1/refactor/includes.js
+++ b/Sprint-1/refactor/includes.js
@@ -1,9 +1,8 @@
 // Refactor the implementation of includes to use a for...of loop
 
 function includes(list, target) {
-  for (let index = 0; index < list.length; index++) {
-    const element = list[index];
-    if (element === target) {
+  for (item of list) {
+    if (item === target) {
       return true;
     }
   }